Demonstrating device



E. P. MOFFITT.

DEMONSTRATING DEVICE.

APPLICATION FILED SEPT- 1. 1920.

1,396,453, Patented Nov. 8, 1921.

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EDW'ARD I. MOFFITT, OF MINNEAPOLIS, MINNESOTA.

DEMONSTRATING DEVICE.

Application filed September To all whom it may concern:

Be it known that I, Enwann P. Morrrr'r, a citizen of the United States. residing at Minneapolis, in the county 01" Hennepin and State of Minnesota, have invented certain new and useful Improvements in Demonstrating Devices, of which the following is a specification.

This invention relates to demonstrating devices, and the object is to provide a simple, clear and easily understood device for illustrating and convincingly demonstrating the principles of a certain type or" phonograph mechanism, such mechanism being disclosed in an application filed by me on March 15th, 1920, under Serial Number 365,908. A further object is to provide means which will by comparison prove the advantage of a certain new form of sound box mounting arrangmentover the older more well known types. In the accompanying drawing:

Figure 1 is a top or plan view of my demonstrating device.

2 is an enlarged sectional view on the line 2-2 in Fig. 1.

Referring to the drawing by reference numerals 3 designates a board or main body on which is pictured the likeness a of a phonograph record, and which has cut therein a radial wedge shaped opening 5. A real record may be secured to the board in place of the representation a it so desired, but in that case it must be mutilated by cutting the radial wedge portion out of it to correspond with the opening 5. Pivoted at the record center by a pin 6 is a suitable radial arm 7 which is adapted to swing freely in the opening 5, and which is pro vided with a series of transverse notches 8. One end of an arm 9 is pivoted at 10 to the board 3, its other end being provided with a stylus 11 adapted to swing in an are through the center 6. A second stylus 1.2 is fixed in a suitable holder 13 in one end of a lever 14. Said lever 14 is pivoted at or near its middle to the arm 9 by a pivot 15. Its other end is pivoted at 16 to one end of an actuating arm 17, said arm 17 having its opposite end pivoted at 18 to the board 3. It is necessary that the distance between the centers 10 and 15 be equal to the distance between the centers 16 and 18, and that the distance between the centers 15 and 16 be substantially twice that between the centers 10 and 18.

In order to fully explain the objects of Specification of Letters Patent.

Patented Nov. 8, 1921.

7, 1920. Serial No. 408,756.

this invention a brief explanation will first be given of the object of the machine it demonstrates and the obstacles it overcomes.

In the commonly constructed forms of sound reproducing machines in which disk records are played, the stylus (as indicated by 11 in the drawing) is fixed in longitudinal position in a sound box on the end of the tone arm (indicated by arm 9). And as the latter swings over the record while playing, the stylus describes an are passing through the center of the record. As the stylus, however, passes over the record it assumes a very diagonal position relative to the groove of the record in which it engages. This position of the needle gives a cramped effect and causes it to tear into one side of the groove, with the result that a perfect tone is not reproduced.

To overcome this difiiculty I invented a device which will cause the position of the needle or stylus (see numeral 12) to at all times assume a direct on tangential to the groove it engages, while it is traveling over the record. In other words the direction of the stylus will always be maintained at right angles from a line drawn from the point of the needle where it engages the record to the center of the record. In this way the needle is permitted to properly engage the undulations in each of the grooves of the record, causing it to reproduce in a scientific manner all of the vibratory movements eX- actly as they were originally recorded in the record.

To properly demonstrate my reproducing arrangement I provided the device hereinafter claimed, in which the stylus 11 represents the old form of mounting and the stylus 12 my improved construction. The tone arm is represented by the bar 9, and the bar 17 corresponds to an actuating bar of similar construction, actuating the bar 14- on which is secured the sound box holding the stylus 12.

The arm 7 illustrates a radial section'of a record, and is made movable and quite thin so as to determine any specific point in said radial section at which a needle is making contact. The notches 8, which are cut at rightangles across the bar 7, represent highly magnified record grooves, comparatively few and only occasional of such grooves being thus shown.

In demonstrating the advantages of the stylus 12 construction over the old form of stylus 11 construction, the arm 7 is brought under the needle points, as shown in the lrawing. It will be noticed that the needle 11 assumes a very diagonal relation to the arm 7 causing it to cut into one side of the groove 8 it may engage, while the direction of the needle 12 is at right angles to the arm or tangential to the groove it may engage. Then by moving the members 9 and '17 toward the center 6, (see dotted lines in Fig. 1) and by moving the arm 7 to the left, to keep it under the stylus points, it will further be noticed that the needle 12 still retains its tangential relation while the needle 11 is still in an angular direction, although this angle approaches a right angle similar to that of stylus 12 as the stylus approaches the center 6. It isnot intended to have the needle 12 travel in a straight radial path across the record. It travels in a curved path, but, with the proportionate distances between the various centers and bearings as above described, it will always assume the tangential direction so necessary for the proper reproduction of the record undulations.

It is understood that suitable modifications may be made in the form and construction of this device if such modifications come within the scope of the appended claims.

Having now therefore fully shown and described my invention .what I claim to be new and desire to protect by Letters Patent is:

1. A demonstrating device of the class described having the simulation of a ph0n0- graph record thereon, a radial arm adapted to swing from the center of said record representation, an arm pivoted atone end to the device and adapted to swing with the other end over the record, said other end having a stylus therein, a second stylus mounted in a lever pivotally secured on said second mentioned arm, an actuating arm pivotally connected at one end to said lever and at the other end to a fixed support.

2. A demonstrating device of the class described having the simulation of a phonograph record thereon, a radial arm adapted to swing from the center of said record representation, said arm having a series of transverse notches therein, an arm pivoted at one end to the device and adapted to swing with the other end over the record, said other end having a stylus therein, a second stylus mounted in a lever pivotally secured on said second mentioned arm, an actuating arm pivotally connected at one end to said lever and at the other end to a fixed support.

3. A device of the class described consistof a suitable body having a wedge shaped opening therein, a mutilated record or simulation thereof on the upper side of said body, the same having its center corresponding with the apex of said opening, two suitably mounted needles adapted to swing simultaneously in varied paths over said opening, a radial member adapted to swing within said opening under said needles.

4:. A device of the class described consisting of a suitable body having a wedge shaped opening therein, a mutilated record 'or simulation thereof, onthe upper side of said body, the same having its center cor responding with the apex of said opening, two suitably mounted needles adapted to swing simultaneously in varied paths over said opening, a radial member adapted to swing within said opening under said needles, means for changing the direction of one of said needles relative to that of the other as said needles swing as described.

In testimony whereof I aflix my signature.

EDWARD P. MOFFITT. 

